-relational operator==(ex const & lh, ex const & rh);
-relational operator!=(ex const & lh, ex const & rh);
-relational operator<(ex const & lh, ex const & rh);
-relational operator<=(ex const & lh, ex const & rh);
-relational operator>(ex const & lh, ex const & rh);
-relational operator>=(ex const & lh, ex const & rh);
-
-/*
-
-// binary relational operators ex with numeric
-relational operator==(ex const & lh, numeric const & rh);
-relational operator!=(ex const & lh, numeric const & rh);
-relational operator<(ex const & lh, numeric const & rh);
-relational operator<=(ex const & lh, numeric const & rh);
-relational operator>(ex const & lh, numeric const & rh);
-relational operator>=(ex const & lh, numeric const & rh);
-
-// binary relational operators numeric with ex
-relational operator==(numeric const & lh, ex const & rh);
-relational operator!=(numeric const & lh, ex const & rh);
-relational operator<(numeric const & lh, ex const & rh);
-relational operator<=(numeric const & lh, ex const & rh);
-relational operator>(numeric const & lh, ex const & rh);
-relational operator>=(numeric const & lh, ex const & rh);
-
-*/
+const relational operator==(const ex & lh, const ex & rh);
+const relational operator!=(const ex & lh, const ex & rh);
+const relational operator<(const ex & lh, const ex & rh);
+const relational operator<=(const ex & lh, const ex & rh);
+const relational operator>(const ex & lh, const ex & rh);
+const relational operator>=(const ex & lh, const ex & rh);